This is about building the kernel and apps using uClinux-dist sources.
If you got any problems, please post over the nios forum.

(This is different from the very old buildroot guide approach. DO NOT MIX UP)

To begin, you must have followed InstallNios2Linux , downloaded the nios2-linux-20080616.tar and checked out the source. Older version dose NOT apply to the procedures described here.

In uClinux-dist dir, perform the menuconfig. DO NOT cd linux-2.6.x
cd uClinux-dist
make menuconfig

In the menuconfig, make sure it is selected as follows:

Vendor/Product Selection --->   # select
    --- Select the Vendor you wish to target
        Vendor (Altera)  --->   # should have default to Altera
    --- Select the Product you wish to target
        Altera Products (nios2)  --->    # should have defaulted to nios2

Kernel/Library/Defaults Selection --->    # select
        (linux-2.6.x) Kernel Version
        Libc Version (None)  --->     # should have defulat to None - very important.
    [*] Default all settings (lose changes)     # select
    [ ] Customize Kernel Settings
    [ ] Customize Vendor/User Settings
    [ ] Update Default Vendor Settings
Then <exit> <exit> <yes>
DO NOT change any other setting until first successful boot.

Run vendor_hwselect to setup the memory and io port address map of your Nios II board (see LinuxHwselect for details) . Select the nios2 cpu and sdram.
(still in uClinux-dist dir, DO NOT cd linux-2.6.x)
make vendor_hwselect SYSPTF=/path_to_your_hardware_project/your_system.ptf  # you must give the absolute path to ptf, no space allowed in path

Compile kernel and apps,
make
(this will take a while)

If you meet errors, you can use "NON_SMP_BUILD=1 make", which avoids parallel make. The messages will be cleaner.

The compressed kernel is stored in the images folder, is called zImage and is in ELF format. You can follow TryOutuClinux to run the new zImage.

In case you want a real clean restart, use "git clean",
git clean -f -x -d

---

Below is the the start up message of an Altera NEEK dev board.

# nios2-download -g images/zImage
Using cable "USB-Blaster [USB 2-1.2]", device 1, instance 0x00
Pausing target processor: OK
Initializing CPU cache (if present)
OK
Downloaded 1272KB in 7.7s (165.1KB/s)
Verified OK                        
Starting processor at address 0x00500000
# nios2-terminal
nios2-terminal: connected to hardware target using JTAG UART on cable
nios2-terminal: "USB-Blaster [USB 2-1.2]", device 1, instance 0
nios2-terminal: (Use the IDE stop button or Ctrl-C to terminate)

Uncompressing Linux... Ok, booting the kernel.
Linux version 2.6.26-rc6 (hippo@darkstar) (gcc version 3.4.6) #2 PREEMPT Mon Jun 16 14:30:09 CST 2008


uClinux/Nios II
Built 1 zonelists in Zone order, mobility grouping off.  Total pages: 8128
Kernel command line:
PID hash table entries: 128 (order: 7, 512 bytes)
Dentry cache hash table entries: 4096 (order: 2, 16384 bytes)
Inode-cache hash table entries: 2048 (order: 1, 8192 bytes)
Memory available: 30136k/2333k RAM, 0k/0k ROM (1552k kernel code, 781k data)
Mount-cache hash table entries: 512
net_namespace: 180 bytes
NET: Registered protocol family 16
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 1024 (order: 1, 8192 bytes)
TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
TCP: Hash tables configured (established 1024 bind 1024)
TCP reno registered
NET: Registered protocol family 1
io scheduler noop registered
io scheduler deadline registered (default)
ttyJ0 at MMIO 0x8009340 (irq = 8) is a Altera JTAG UART
console [ttyJ0] enabled
ttyS0 at MMIO 0x8008e00 (irq = 7) is a Altera UART
dm9000 Ethernet Driver, V1.30
TCP cubic registered
NET: Registered protocol family 17
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
Freeing unused kernel memory: 572k freed (0x1b8000 - 0x246000)
Shell invoked to run file: /etc/rc
Command: hostname uClinux
Command: mount -t proc proc /proc
Command: mount -t sysfs sysfs /sys
Command: mount -t usbfs none /proc/bus/usb
mount: mounting none on /proc/bus/usb failed: No such file or directory
Command: mkdir /var/tmp
Command: mkdir /var/log
Command: mkdir /var/run
Command: mkdir /var/lock
Command: mkdir /var/empty
Command: ifconfig lo 127.0.0.1
Command: route add -net 127.0.0.0 netmask 255.0.0.0 lo
Command: cat /etc/motd
Welcome to
          ____ _  _
         /  __| ||_|                
    _   _| |  | | _ ____  _   _  _  _
   | | | | |  | || |  _ \| | | |\ \/ /
   | |_| | |__| || | | | | |_| |/   
   |  ___\____|_||_|_| |_|\____|\_/\_/
   | |
   |_|

For further information check:
http://www.uclinux.org/

Execution Finished, Exiting

Sash command shell (version 1.1.1)
/>

---

Now, you can config uClinux-dist for costmize kernel and select your apps. I enabled only SMC91C111 and DM9000  Ethernet device drivers for Altera dev board in default config, you should enable your EtherNet driver in kernel config otherwise. see LinuxConfig for kernel config items.

Still in uClinux-dist dir, DO NOT cd linux-2.6.x

make menuconfig

Kernel/Library/Defaults Selection --->
(linux-2.6.x) Kernel Version
(None) Libc Version
[ ] Default all settings (lose changes)
[*] Customize Kernel Settings    <== to change kernel config
[*] Customize Vendor/User Settings  <== to change user apps config
[ ] Update Default Vendor Settings

Then <exit> <exit> <yes> .
It will enter kernel config first,  then it will enter user apps config, you can select more apps.
After you change config,

make

---

You may want to now run your own program on the uClinux system.

An example Hello World program is here: CompileHello

There are more example programs linked under Then More Fun here: µClinux

---

Here is more usage about uClinux,

/> ifconfig eth0 192.168.1.85  # staic ip
/> route add default gw 192.168.1.254     # gateway
/> ifconfig
eth0      Link encap:Ethernet  HWaddr 00:07:ED:00:00:00 
          inet addr:192.168.1.85  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST NOTRAILERS RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2260 (2.2 KiB)  TX bytes:2854 (2.7 KiB)
          Interrupt:8

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

/> inetd &  # start inetd to invoke telnetd and ftpd services
[22]
/> boa &  # start httpd with cgi-demo
[23]
/> netstat -a  # show network services
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State     
tcp        0      0 *:http                  *:*                     LISTEN     
tcp        0      0 *:ftp                   *:*                     LISTEN     
tcp        0      0 *:telnet                *:*                     LISTEN     
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path
/> free
MemTotal:         6520 kB
MemFree:          4340 kB
Buffers:             0 kB
/> ps
  PID PORT STAT  SIZE SHARED %CPU COMMAND
    1      S     147K     0K  2.8 /init
    2      S       0K     0K  0.0 ksoftirqd/0
    3      S       0K     0K  0.0 events/0
    4      S       0K     0K  0.0 khelper
    5      S       0K     0K  0.0 kthread
    6      S       0K     0K  0.0 kblockd/0
    7      S       0K     0K  0.0 pdflush
    8      S       0K     0K  0.0 pdflush
    9      S       0K     0K  0.0 kswapd0
   10      S       0K     0K  0.0 aio/0
   17      R     147K     0K  0.3 -/bin/sh
   19      S     147K     0K  0.2 dhcpcd
   22      S      95K     0K  0.1 inetd
   23      S     275K     0K  0.4 boa
/>

ftpd usage, user : ftp, password: <anything> , dir : /home/ftp
boa and cgi usage, dir : /home/httpd

You can check what is in busybox, by running "busybox" on uClinux.
You can check what is in sash, by "help" .

We use initramfs instead of the default romfs . The initramfs is generated from romfs dir and the dev file in vendors/Altera/nios2/romfs_list . See InitramfsUpdate .

The simplified "init" program will run etc/rc and etc/inittab during startup.
If you want to customize startup, eg inet servers and eth config, you should update the files vendors/Altera/nios2/ rc and inittab.

We arrange to minimize the memory usage. We use sash as default shell, it is smaller than busybox and take less memory. We include some standalone networking servers, such as inetd and telnetd. We build some networking utility into busybox, such as ifconfig,route,netstat,telnet,wget..etc. We don't use sh in busybox, and don't use servers in busybox as it takes a lot of memory.

You may use the simple history in sash. Use "h" to list history. Use "!<d>" , d=1..20, to recall one of the history, eg "!3" for the 3rd cmd line.

Use control-H for backspace.
/> h
 1: netstat -a
 2: date
 3: ntpdate pool.ntp.org
 4: date
 5: boa &
 6: inetd &
 7: ifconfig
 8: dhcpcd &
 9: free
10: ps
/> !10
  PID PORT STAT  SIZE SHARED %CPU COMMAND
    1      S     147K     0K  1.7 /init
    2      S       0K     0K  0.0 ksoftirqd/0
    3      S       0K     0K  0.0 events/0
    4      S       0K     0K  0.0 khelper
    5      S       0K     0K  0.0 kthread
    6      S       0K     0K  0.0 kblockd/0
    7      S       0K     0K  0.0 pdflush
    8      S       0K     0K  0.0 pdflush
    9      S       0K     0K  0.0 kswapd0
   10      S       0K     0K  0.0 aio/0
   11      S       0K     0K  0.0 mtdblockd
   18      R     147K     0K  0.1 /bin/sh
   19      S     147K     0K  0.0 dhcpcd
   22      S      95K     0K  0.0 inetd
   23      S     275K     0K  0.0 boa
/>

update git to the latest

After you have first successful boot, you may use "git pull" to update the kernel and uClinux-dist. Please refer to GitServer .
cd uClinux-dist
git pull
cd ..
cd linux-2.6
git pull
cd ..